<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.14/dist/vue.js"></script>
</head>
<body>
    <div id="root">
        姓：<input type="text" v-model="firstName"><br/><br/>
        名：<input type="text" v-model="lastName"><br/><br/>
        姓名：<span>{{fullName()}}</span>
    </div>
    <script>
        new Vue({
            el:"#root",
            data:{
                firstName:'张',
                lastName:'三'
            },
            methods: {
                fullName(){
                    return this.firstName+this.lastName
                }
            },
        })
    </script>
</body>
</html>